Renal denervation balloon catheter with ride along electrode support

ABSTRACT

A renal nerve ablation device may include an elongate tubular member having a distal region. An expandable member may be coupled to the distal region. An electrode support may be coupled to the distal region of the elongate tubular member and extend over a body of the expandable member. The electrode support may be free of connection to the body of the expandable member. One or more electrodes may be coupled to the electrode support.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to U.S.Provisional Application Ser. No. 61/838,086, filed Jun. 21, 2013, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods forusing and manufacturing medical devices. More particularly, the presentdisclosure pertains to medical devices for renal nerve ablation.

BACKGROUND

A wide variety of intracorporal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

A medical device for renal nerve ablation may include a catheter shaft,an expandable member coupled to the catheter shaft, the expandablemember having a proximal region, a distal region, and a body extendingtherebetween. The medical device may further include an electrodesupport coupled to the catheter shaft and positioned over the body ofthe expandable member, the electrode support including a plurality offlexible elongate members and a plurality of electrode assembliesdisposed on the elongate members, the electrode support capable ofexpanding with the expandable member, wherein the electrode support isfree from attachment with the body of the expandable member.

A medical device may include a catheter shaft, an expandable balloon, aflexible elongate electrode assembly, and a plurality of electrodeelements. The expandable balloon may have a distal waist, proximalwaist, and a body extending therebetween, the proximal waist beingcoupled to the catheter shaft. The flexible elongate electrode assemblymay be coupled to the catheter shaft and may extend in a helix over thebody of the expandable balloon, the electrode assembly free fromattachment to the body of the expandable balloon. The plurality ofelectrode elements may be disposed on the flexible elongate electrodeassembly.

A method for treating hypertension may include providing a medicaldevice, the medical device including a catheter shaft, an expandablemember coupled to the catheter shaft, an expandable electrode supportcoupled to the catheter shaft and positioned over the expandable member,the electrode support including a plurality of flexible elongate membersand a plurality of electrode assemblies disposed on the elongatemembers, the electrode support capable of expanding with the expandablemember, wherein the electrode support is free from attachment with theexpandable member, and a delivery sheath. The method may further includethe steps of advancing the medical device through a blood vessel to aposition within a renal artery, expanding the expandable member, therebyexpanding the electrode support, energizing the electrode assemblies,collapsing the expandable member, and thereafter, withdrawing theexpandable member and the electrode support into the delivery sheath,thereby collapsing the electrode support.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic view of an example renal nerve ablation device;

FIG. 2 is a perspective view of an example expandable member of a renalnerve ablation device;

FIG. 3 is a partial top view of the expandable member of FIG. 2 in anunrolled or flat configuration;

FIG. 4 is a top view of a portion of an example electrode assembly;

FIG. 5 is a partial cross-sectional view A-A of FIG. 4;

FIG. 6 is a partial cross-sectional view B-B of FIG. 4;

FIG. 7 is a perspective view of an example renal nerve ablation device;

FIG. 8 is a perspective view of the electrode support of FIG. 7;

FIG. 9 is a perspective view of an example expandable member;

FIG. 10 is an end view of the expandable member of FIG. 9;

FIG. 11 is a perspective view of the expandable member of FIG. 9 with anelectrode support;

FIG. 12 is a perspective view of another example renal nerve ablationdevice;

FIG. 13 is a partial top view of the electrode support of FIG. 12 in anunrolled or flat configuration;

FIG. 14 is a perspective view of another example renal nerve ablationdevice; and

FIG. 15 is a perspective view of another example renal nerve ablationdevice.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the invention tothe particular embodiments described. On the contrary, the intention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings,which are not necessarily to scale, wherein like reference numeralsindicate like elements throughout the several views. The detaileddescription and drawings are intended to illustrate but not limit theclaimed invention. Those skilled in the art will recognize that thevarious elements described and/or shown may be arranged in variouscombinations and configurations without departing from the scope of thedisclosure. The detailed description and drawings illustrate exampleembodiments of the claimed invention.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about”, in thecontext of numeric values, generally refers to a range of numbers thatone of skill in the art would consider equivalent to the recited value(i.e., having the same function or result). In many instances, the term“about” may include numbers that are rounded to the nearest significantfigure. Other uses of the term “about” (i.e., in a context other thannumeric values) may be assumed to have their ordinary and customarydefinition(s), as understood from and consistent with the context of thespecification, unless otherwise specified.

The recitation of numerical ranges by endpoints includes all numberswithin that range, including the endpoints (e.g. 1 to 5 includes 1, 1.5,2, 2.75, 3, 3.80, 4, and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment(s) described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it would be within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments, whether or not explicitlydescribed, unless clearly stated to the contrary. That is, the variousindividual elements described below, even if not explicitly shown in aparticular combination, are nevertheless contemplated as being combinedor arranged with each other to form other additional embodiments or tocomplement and/or enrich the described embodiment(s), as would beunderstood by one of ordinary skill in the art.

Certain treatments are aimed at the temporary or permanent interruptionor modification of select nerve function. One example treatment is renalnerve ablation, which is sometimes used to treat conditions such as orrelated to hypertension, congestive heart failure, diabetes, or otherconditions impacted by high blood pressure or salt retention. Thekidneys produce a sympathetic response, which may increase the undesiredretention of water and/or sodium. The result of the sympatheticresponse, for example, may be an increase in blood pressure. Ablatingsome of the nerves running to the kidneys (e.g., disposed adjacent to orotherwise along the renal arteries) may reduce or eliminate thissympathetic response, which may provide a corresponding reduction in theassociated undesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generatingand control apparatus, often for the treatment of targeted tissue inorder to achieve a therapeutic effect. In some embodiments, the targettissue is tissue containing or proximate to nerves, including renalarteries and associated renal nerves. In other embodiments the targettissue is luminal tissue, which may further comprise diseased tissuesuch as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliverenergy in a targeted dosage may be used for nerve tissue in order toachieve beneficial biologic responses. For example, chronic pain,urologic dysfunction, hypertension, and a wide variety of otherpersistent conditions are known to be affected through the operation ofnervous tissue. For example, it is known that chronic hypertension thatmay not be responsive to medication may be improved or eliminated bydisabling excessive nerve activity proximate to the renal arteries. Itis also known that nervous tissue does not naturally possessregenerative characteristics. Therefore it may be possible tobeneficially affect excessive nerve activity by disrupting theconductive pathway of the nervous tissue. When disrupting nerveconductive pathways, it is particularly advantageous to avoid damage toneighboring nerves or organ tissue. The ability to direct and controlenergy dosage is well-suited to the treatment of nerve tissue. Whetherin a heating or ablating energy dosage, the precise control of energydelivery as described and disclosed herein may be directed to the nervetissue. Moreover, directed application of energy may suffice to target anerve without the need to be in exact contact, as would be required whenusing a typical ablation probe. For example, eccentric heating may beapplied at a temperature high enough to denature nerve tissue withoutcausing ablation and without requiring the piercing of luminal tissue.However, it may also be desirable to configure the energy deliverysurface of the present disclosure to pierce tissue and deliver ablatingenergy similar to an ablation probe with the exact energy dosage beingcontrolled by a power control and generation apparatus.

In some embodiments, efficacy of the denervation treatment can beassessed by measurement before, during, and/or after the treatment totailor one or more parameters of the treatment to the particular patientor to identify the need for additional treatments. For instance, adenervation system may include functionality for assessing whether atreatment has caused or is causing a reduction in neural activity in atarget or proximate tissue, which may provide feedback for adjustingparameters of the treatment or indicate the necessity for additionaltreatments.

While the devices and methods described herein are discussed relative torenal nerve ablation and/or modulation, it is contemplated that thedevices and methods may be used in other treatment locations and/orapplications where nerve modulation and/or other tissue modulationincluding heating, activation, blocking, disrupting, or ablation aredesired, such as, but not limited to: blood vessels, urinary vessels, orin other tissues via trocar and cannula access. For example, the devicesand methods described herein can be applied to hyperplastic tissueablation, cardiac ablation, pulmonary vein isolation, pulmonary veinablation, tumor ablation, benign prostatic hyperplasia therapy, nerveexcitation or blocking or ablation, modulation of muscle activity,hyperthermia or other warming of tissues, etc.

FIG. 1 is a schematic view of an example renal nerve ablation system100. System 100 may include a renal nerve ablation device 120. Renalnerve ablation device 120 may be used to ablate nerves (e.g., renalnerves) disposed adjacent to the kidney K (e.g., renal nerves disposedabout a renal artery RA). In use, renal nerve ablation device 120 may beadvanced through a blood vessel such as the aorta A to a position withinthe renal artery RA. This may include advancing renal nerve ablationdevice 120 through a guide sheath or catheter 14. When positioned asdesired, renal nerve ablation device 120 may be activated to activateone or more electrodes (not shown). This may include operativelycoupling renal nerve ablation device 120 to a control unit 110, whichmay include an RF generator, so as to supply the desired activationenergy to the electrodes. For example, renal nerve ablation device 120may include a wire or conductive member 18 with a connector 20 that canbe connected to a connector 22 on the control unit 110 and/or a wire 24coupled to the control unit 110. In at least some embodiments, thecontrol unit 110 may also be utilized to supply/receive the appropriateelectrical energy and/or signal to activate one or more sensors disposedat or near a distal end of renal nerve ablation device 120. Whensuitably activated, the electrodes may be capable of ablating tissue(e.g., renal nerves) as described below and the sensors may be used todetect desired physical and/or biological parameters.

An exemplary control unit 110 and associated energy delivery methodsuseable with the embodiments disclosed herein are disclosed in U.S.Patent Application Publication No. 2012/0095461 entitled “PowerGenerating and Control Apparatus for the Treatment of Tissue”, the fulldisclosure of which is incorporated by reference herein. Furtherexamples useable with the embodiments disclosed herein are disclosed inU.S. Pat. No. 7,742,795 entitled “Tuned RF Energy for SelectiveTreatment of Atheroma and Other Target Tissues and/or Structures”, U.S.Pat. No. 7,291,146 entitled “Selectable Eccentric Remodeling and/orAblation of Atherosclerotic Material”, and U.S. Patent ApplicationPublication No. 2008/0188912 entitled “System for Inducing DesirableTemperature Effects on Body Tissue”, the full disclosures of which areincorporated herein by reference. In some embodiments, particularly insome embodiments utilizing monopolar energy delivery, the system 100 mayalso include a ground/common electrode (not shown), which may beassociated with the ablation device 120. The ground/common electrode maybe a separate pad that is electrically or otherwise operatively coupledto the control unit 110, or otherwise associated with the system 100.

In some embodiments, the control unit 110 may include a processor orotherwise be coupled to a processor to control or record treatment. Theprocessor may typically comprise computer hardware and/or software,often including one or more programmable processor units runningmachine-readable program instructions or code for implementing some, orall, of one or more of the embodiments and methods described herein. Thecode may often be embodied in a tangible media such as a memory(optionally a read-only memory, a random access memory, a non-volatilememory, or the like) and/or a recording media (such as a floppy disk, ahard drive, a CD, a DVD, or other optical media, a non-volatilesolid-state memory card, or the like). The code and/or associated dataand signals may also be transmitted to or from the processor via anetwork connection (such as a wireless network, an ethernet, aninternet, an intranet, or the like), and some or all of the code mayalso be transmitted between components of a renal nerve ablation systemand within the processor via one or more buses, and appropriate standardor proprietary communications cards, connectors, cables, and the likemay often be included in the processor. The processor may often beconfigured to perform the calculations and signal transmission stepsdescribed herein at least in part by programming the processor with thesoftware code, which may be written as a single program, a series ofseparate subroutines or related programs, or the like. The processor maycomprise standard or proprietary digital and/or analog signal processinghardware, software, and/or firmware, and may desirably have sufficientprocessing power to perform the calculations described herein duringtreatment of the patient, the processor may optionally comprise apersonal computer, a notebook computer, a tablet computer, a proprietaryprocessing unit, or a combination thereof. Standard or proprietary inputdevices (such as a mouse, keyboard, touchscreen, joystick, etc.) andoutput devices (such as a printer, speakers, display, etc.) associatedwith modern computer systems may also be included, and processors havinga plurality of processing units (or even separate computers) may beemployed in a wide range of centralized or distributed data processingarchitectures.

In some embodiments, control software for the system 100 may use aclient-server scheme to further enhance system ease of use, flexibility,and reliability. “Clients” may be the system control logic; “servers”may be the control hardware. A communications manager may deliverchanges in system conditions to subscribing clients and servers. Clientsmay “know” what the present system condition is, and what command ordecision to perform based on a specific change in condition. Servers mayperform the system function based on client commands. Because thecommunications manager may be a centralized information manager, newsystem hardware may not require changes to prior existing client-serverrelationships; new system hardware and its related control logic maythen merely become an additional “subscriber” to information managedthrough the communications manager. This control schema may provide thebenefit of having a robust central operating program with base routinesthat are fixed; no change to base routines may be necessary in order tooperate new circuit components designed to operate with the system.

In some embodiments, the renal nerve ablation device 120 may include anelongate tubular member or catheter shaft 122, as shown in FIG. 2. Insome embodiments, the elongate tubular member or catheter shaft 122 maybe configured to be slidingly advanced over a guidewire or otherelongate medical device to a target site. In some embodiments, theelongate tubular member or catheter shaft 122 may be configured to beslidingly advanced within a guide sheath or catheter 14 to a targetsite. In some embodiments, the elongate tubular member or catheter shaft122 may be configured to be advanced to a target site over a guidewire,within a guide sheath or catheter 14, or a combination thereof.

An expandable member 130 may be disposed at, on, about, or near a distalregion of the elongate tubular member or catheter shaft 122. Theexpandable member 130 may have a body 135, a proximal waist 136, and adistal waist 137. In some embodiments, the expandable member 130 may befixedly attached to the elongate tubular member or catheter shaft 122.In some embodiments the proximal waist 136 and the distal waist 137 areattached to the catheter shaft 122 while the body 135 is free fromattachment to the catheter shaft 122. In some embodiments, theexpandable member 130 may be self-expanding from a collapsed deliverystate to an expanded state, such as a basket, a swellable foam or othermaterial, or a plurality of struts, for example. In some embodiments,the expandable member 130 may be selectively expanded from a collapseddelivery state to an expanded state, such as a compliant, non-compliant,or semi-compliant balloon, for example. In some embodiments, one or moreelectrodes may be disposed on, disposed about, or coupled to an outersurface of the expandable member 130. In some embodiments, the one ormore electrodes may be operatively and/or electrically connected to thecontrol unit 110 and/or the RF generator. In some embodiments, the oneor more electrodes may include a plurality of electrode assemblies. Insome embodiments, one or more of the plurality of electrode assembliesmay be configured to be monopolar or bipolar, and may further include atemperature sensor, for example, a thermistor or thermocouple.

For example, as shown in FIG. 2, in some embodiments, the electrodeassemblies may be arranged on the expandable member 130, shown here inan expanded state, according to a plurality of generally cylindricaltreatment zones A-D. In other embodiments, the expandable member 130 orother components of the treatment system may include additionalelectrode assemblies that are not in a treatment zone or are otherwisenot used or configured to deliver a treatment energy.

The treatment zones A-D and associated electrode assemblies 140 a-d arefurther illustrated in FIG. 3, which is an “unrolled” depiction of aportion of the expandable member 130 of FIG. 2. In some embodiments, theexpandable member may be a balloon with a 4 mm diameter and twoelectrode assemblies 140 a-b. In other embodiments, the expandablemember may be a balloon with a 5 mm diameter and three electrodeassemblies 140 a-c. In some embodiments, the expandable member may be aballoon with a 6, 7, or 8 mm diameter and four electrode assemblies 140a-d, as depicted in FIG. 2. For any of these configurations, theexpandable member may have a working length of about 10 mm to about 100mm, or about 18 mm to about 25 mm, which may be the approximatelongitudinal span of all the treatment zones A-D shown in FIGS. 2 and 3.The electrode assemblies 140 a-d may be attached to a balloon usingadhesive, or other suitable means.

Returning to FIG. 2, the treatment zones A-D may be longitudinallyadjacent to one another along longitudinal axis L-L, and may beconfigured such that energy applied by the electrode assemblies createtreatments that do not overlap. Treatments applied by the longitudinallyadjacent bipolar electrode assemblies 140 a-d may be circumferentiallynon-continuous along longitudinal axis L-L. For example, with referenceto FIG. 3, lesions created in treatment zone A may in some embodimentsminimize overlap about a circumference (laterally with respect to L-L inthis view) with lesions created in treatment zone B. In otherembodiments, however, the energy applied by the electrode assemblies,such as the electrode assemblies shown in FIG. 3, may overlap,longitudinally, circumferentially, and/or in other ways, to at leastsome extent.

Whether or not treatment zones between electrodes/electrode pairs willoverlap may be influenced by a wide variety of factors, including, butnot limited to, electrode geometry, electrode placement density,electrode positioning, ground/common electrode(s) placement and geometry(in monopolar embodiments), energy generator output settings, outputvoltage, output power, duty cycle, output frequency, tissuecharacteristics, tissue type, etc. In some embodiments, individualelectrodes of a bipolar electrode pair may each define its own treatmentzone, and such treatment zones may partially or entirely overlap. Insome embodiments, the overlap of treatment zones may extendsubstantially continuously around a circumference of the expandablemember and/or around a circumference in a tissue surrounding a bodypassageway. In other embodiments, there may be overlap in treatmentzones, however, that overlap may not be substantially continuous arounda circumference and significant discontinuities in the treatment zonesmay be present.

Returning to FIG. 3, each electrode pad assembly may include four majorelements, which are a distal electrode pad 150 a-d, intermediate tail160 a-d, proximal electrode pad 170 a-d, and proximal tail 180 b,d (notshown for electrode pad assemblies 140 b and 140 c). Constructionaldetails of the electrode assemblies 140 a-d are shown and described withreference to FIGS. 4-6.

FIG. 4 shows a top view of electrode assembly 200, which is identifiedin FIG. 3 as electrode assembly 140. The electrode assembly 200 may beconstructed as a flexible circuit having a plurality of layers. Suchlayers may be continuous or non-contiguous, i.e., made up of discreteportions. Shown in FIGS. 5 and 6, a base layer 202 of insulation mayprovide a foundation for the electrode assembly 200. The base layer 202may be constructed from a flexible polymer such as polyimide, althoughother materials are contemplated. In some embodiments, the base layer202 may be from about 0.01 mm thick to about 0.02 mm thick. In someembodiments, the base layer 202 may be approximately 0.5 mil (0.0127 mm)thick. A conductive layer 204 made up of a plurality of discrete tracesmay be layered on top of the base layer 202. The conductive layer 204may be, for example, a layer of electrodeposited copper. Other materialsare also contemplated. In some embodiments, the conductive layer 204 maybe from about 0.01 mm thick to about 0.02 mm thick. In some embodiments,the conductive layer 204 may be approximately 0.5 mil (0.018 mm) thick.An insulating layer 206 may be discretely or continuously layered on topof the conductive layer 204, such that the conductive layer 204 may befluidly sealed between the base layer 202 and the insulating layer 206.Like the base layer 202, the insulating layer 206 may be constructedfrom a flexible polymer such as polyimide, although other materials arecontemplated. In some embodiments, the insulating layer 206 may be fromabout 0.01 mm thick to about 0.02 mm thick. In some embodiments, theinsulating layer 206 may be approximately 0.5 mil (0.0127 mm) thick. Inother embodiments, the insulating layer 206 may be a complete or partialpolymer coating, such as PTFE or silicone. Other materials are alsocontemplated.

The electrode assembly 200 shown in FIG. 4 may include a distalelectrode pad 208. In this region, the base layer 202 may form arectangular shape. This is not intended to be limiting. Other shapes arecontemplated. As shown, the electrode assembly 200 may include aplurality of openings to provide for added flexibility, and the pads andother portions of the assemblies may include rounded or curved corners,transitions and other portions. In some instances, the openings androunded/curved features may enhance the assembly's resistance todelamination from its expandable device, as may occur, in someinstances, when the expandable device is repeatedly expanded andcollapsed (which may also entail deployment from and withdrawal into aprotective sheath), such as may be needed when multiple sites aretreated during a procedure.

The distal electrode pad 208 may include a plurality of discrete traceslayered on top of the base layer 202. These traces may include a groundtrace 210, an active electrode trace 212, and a sensor trace 214. Theground trace 210 may include an elongated electrode support 216laterally offset from a sensor ground pad 218. The sensor ground pad 218may be electrically coupled to the elongated electrode support 216 ofthe ground trace 210 and may be centrally located on the distalelectrode pad 208. A bridge 220 may connect a distal most portion of thesensor ground pad 218 to a distal portion of the elongated electrodesupport 216 of the ground trace 210. The bridge 220 may taper down inwidth as it travels to the sensor ground pad 218. In some embodiments,the bridge 220 may have a relatively uniform and thin width to enable adesired amount of flexibility. The elongated electrode support 216 maytaper down in width at its proximal end, however, this is not required.In some embodiments, the elongated electrode support 216 may abruptlytransition to a much thinner trace at its proximal portion, to enable adesired amount of flexibility. Generally, the curvature of the traceswhere necking is shown may be optimized to reduce balloon recaptureforces and the potential for any snagging that sharper contours maypresent. The shape and position of the traces may also be optimized toprovide dimensional stability to the electrode assembly 200 as a whole,so as to prevent distortion during deployment and use.

The ground trace 210 and active electrode trace 212 of FIG. 4 may sharea similar construction. The active electrode trace 212 may also includean elongated electrode support 216.

FIG. 5 shows a partial cross-section A-A of the distal electrode pad208. An electrode 222 is shown layered over a portion of the insulatinglayer 206, which may have a plurality of passages (e.g., holes) toenable the electrode 222 to couple to the elongated electrode support216 of the ground trace 210 (of conductive layer 204).

As shown in FIG. 4, the ground electrode trace 210 and active electrodetrace 212 may include a plurality of electrodes. Three electrodes 222may be provided for each electrode trace, however, more or less may beused. Additionally, each electrode 222 may have radiused corners toreduce tendency to snag on other devices and/or tissue. Although theabove description of the electrodes 222 and the traces associated withthem has been described in the context of a bi-polar electrode assembly,those of skill in the art will recognize that the same electrodeassembly may function in a monopolar mode as well. For instance, as onenon-limiting example, the electrodes associated with active electrodetraces 212 and 242 may be used as monopolar electrodes, with groundtrace 210 disconnected during energization of those electrodes.

In some embodiments, as shown in FIG. 4 for example, each electrode 222may be approximately 1.14 mm by 0.38 mm, with approximately 0.31 mm gapslying between the electrodes 222. The electrodes 222 of the ground trace210 and active electrode trace 212 may be laterally spaced byapproximately 1.85 mm. In some embodiments, as shown in FIG. 5 forexample, the electrodes 222 may be gold pads approximately 0.038 mmthick from the conductive layer 204 and that may protrude about 0.025 mmabove the insulating layer 206. Without limiting the use of other suchsuitable materials, gold may be a good electrode material because it isvery biocompatible, radiopaque, and electrically and thermallyconductive. In other embodiments, the electrode thickness of theconductive layer 204 may range from about 0.030 mm to about 0.051 mm. Atsuch thicknesses, relative stiffness of the electrodes 222, as comparedto, for example, the copper conductive layer 204, may be high. Becauseof this, using a plurality of electrodes, as opposed to a singleelectrode, may increase flexibility. In other embodiments, theelectrodes may be as small as about 0.5 mm by about 0.2 mm or as largeas about 2.2 mm by about 0.6 mm for electrode 222.

While it may be an important design optimization consideration tobalance the thickness of the gold above the insulating layer 206 so asto achieve good flexibility while maintaining sufficient height so as toprovide good tissue contact, this may be counterbalanced with the goalof avoiding a surface height that may snag during deployment or collapseof the balloon. These issues may vary according to other elements of aparticular procedure, such as balloon pressure. For many embodiments, ithas been determined that electrodes that protrude approximately 0.025 mmabove the insulating layer 206 will have good tissue contact at ballooninflation pressures below 10 atm and as low as 2 atm. These pressuresmay be well below the typical inflation pressure of an angioplastyballoon.

The sensor trace 214 may be centrally located on the distal electrodepad 208 and may include a sensor power pad 224 facing the sensor groundpad 218. These pads may connect to power and ground poles of atemperature sensor 226, such as a thermocouple (for example, Type Tconfiguration: Copper/Constantan) or thermistor, as shown in the partialcross-section depicted in FIG. 6.

The temperature sensor 226 may be proximately connected to the sensorpower pad 224 and may be distally connected to the sensor ground pad218. To help reduce overall thickness, the temperature sensor 226 may bepositioned within an opening within the base layer 202. In someembodiments, the temperature sensor 226 may be a thermistor having athickness of about 0.1 mm, which is unusually thin—approximatelytwo-thirds of industry standard. As shown, the temperature sensor 226may be on a non-tissue contacting side of the distal electrode pad 208.Accordingly, the temperature sensor 226 may be captured between theelectrode structure and a balloon when incorporated into a final device,such as ablation device 120. This may be advantageous sincesurface-mounted electrical components, like thermistors, typically havesharp edges and corners, which may get caught on tissue and possiblycause problems in balloon deployment and/or retraction. This arrangementmay also keep soldered connections from making contact with blood, sincesolder is typically non-biocompatible. Further, due to the placement ofthe temperature sensor, it may measure temperature representative oftissue and the electrodes 222.

From the distal electrode pad 208, the combined base layer 202,conductive layer 204, and insulating layer 206 may reduce in lateralwidth to an intermediate tail 228. Here, the conductive layer 204 may beformed to include an intermediate ground line 230, intermediate activeelectrode line 232, and intermediate sensor line 234, which may berespectively coextensive traces of the ground trace 210, activeelectrode trace 212, and sensor trace 214 of the distal electrode pad208.

From the intermediate tail 228, the combined base layer 202, conductivelayer 204, and insulating layer 206 may increase in lateral width toform a proximal electrode pad 236. The proximal electrode pad 236 may beconstructed similarly to the distal electrode pad 208, with theelectrode geometry and temperature sensor arrangement being essentiallyidentical, although various differences may be present. However, asshown, the proximal electrode pad 236 may be laterally offset from thedistal electrode pad 208 with respect to a central axis G-G extendingalong the intermediate ground line 230. The intermediate activeelectrode line 232 and intermediate sensor line 234 may be laterallycoextensive with the proximal electrode pad 236 on parallel respectiveaxes with respect to central axis G-G.

From the proximal electrode pad 236, the combined base layer 202,conductive layer 204, and insulating layer 206 may reduce in lateralwidth to form a proximal tail 238. The proximal tail 238 may include aproximal ground line 240, proximal active electrode line 242, andproximal sensor line 244, as well the intermediate active electrode line232 and intermediate sensor line 234. The proximal tail 238 may includeconnectors (not shown) to enable coupling to one or more sub-wiringharnesses and/or connectors and ultimately to control unit 110. Each ofthese lines may be extended along parallel respective axes with respectto central axis G-G.

As shown, the electrode assembly 200 may have an asymmetric arrangementof the distal electrode pad 208 and proximal electrode pad 236, aboutaxis G-G. Further, the ground electrodes of both electrode pads may besubstantially aligned along axis G-G, along with the intermediate andproximal ground lines 230/240. It has been found that this arrangementmay present certain advantages. For example, by essentially sharing thesame ground trace, the width of the proximal tail may be only about oneand a half times that of the intermediate tail 228, rather than beingapproximately twice as wide if each electrode pad had independent groundlines. Thus, the proximal tail 238 may be narrower than two of theintermediate tails 228.

Further, arranging the electrode pads to share a ground trace may allowcontrol of which electrodes will interact with each other. This may notbe immediately apparent when viewing a single electrode assembly, butmay become evident when more than one electrode assembly 200 isassembled onto an expandable member, such as a balloon, for example asshown in FIG. 3. The various electrode pads may be fired and controlledusing solid state relays and multiplexing with a firing time rangingfrom about 100 microseconds to about 200 milliseconds or about 10milliseconds to about 50 milliseconds. For practical purposes, theelectrode pads may appear to be simultaneously firing yet stray currentbetween adjacent electrode pads of different electrode assemblies 200may be prevented by rapid firing of electrodes in micro bursts. This maybe performed such that adjacent electrode pads of different electrodepad assemblies 200 are fired out of phase with one another. Thus, theelectrode pad arrangement of the electrode assembly may allow for shorttreatment times—about 10 minutes or less of total electrode firing time,with some approximate treatment times being as short as about 10seconds, with an exemplary embodiment being about 30 seconds. Somebenefits of short treatment times may include minimization ofpost-operative pain caused when nerve tissue is subject to energytreatment, shortened vessel occlusion times, reduced occlusion sideeffects, and quick cooling of collateral tissues by blood perfusion dueto relatively minor heat input to luminal tissue.

In some embodiments, the common ground may typically carry 200 VAC at500 kHz coming from the negative electrode pole, and a 1V signal fromthe temperature sensor 226 (in the case of a thermistor) that mayrequire filtering of the RF circuit such that the thermistor signal maybe sensed and used for generator control. In some embodiments, becauseof the common ground, the thermistor of the adjacent electrode pair maybe used to monitor temperature even without firing the adjacentelectrode pair. This may provide the possibility of sensing temperaturesproximate to both the distal electrode pad 208 and the proximalelectrode pad 236, while firing only one of them.

Referring again to FIG. 3, the electrode pad arrangement of eachelectrode assembly 140 a-d may also enable efficient placement on theexpandable member 130. As shown, the electrode assemblies 140 a-d may“key” into one another to enable maximum use of the expandable membersurface area. This may be accomplished in part by spacing the electrodepads apart by setting the longitudinal length of each intermediate tail.For example, the intermediate tail length electrode assembly 140 a maybe set to a distance that separates its distal and proximal electrodepads 150 a, 170 a such that the laterally adjacent proximal electrodepad 170 b of the laterally adjacent electrode pad assembly 140 b keysnext to the intermediate tail 160 a of electrode pad assembly 140 a.Further, the distal electrode pad 150 a of electrode assembly 140 a maybe keyed between the intermediate tail 160 b of electrode assembly 140 band the intermediate tail 160 d of electrode assembly 140 d. Thus, thelength of each intermediate tail 160 a-d may also require each electrodepad of any one electrode assembly to be located in non-adjacenttreatment zones.

Expandable member or balloon surface area maximization may also beenabled in part by laterally offsetting both electrode pads of eachelectrode assembly 140 a-d. For example, the rightwards lateral offsetof each distal electrode pad 150 a-d and the leftwards lateral offset ofthe proximal electrode pad 170 a-d allow adjacent electrode padassemblies to key into one another such that some of the electrode padsmay laterally overlap one another. For example, the distal electrode pad150 a of electrode assembly 140 a may laterally overlap with proximalelectrode pad 170 b of electrode assembly 140 b. Further, the distalelectrode pad 150 b of electrode assembly 140 b may laterally overlapwith the proximal electrode pad 170 c of electrode assembly 140 c.However, the length of each intermediate tail may preventcircumferential overlap (longitudinal overlap in this view) of theelectrode pads, thus maintaining the non-contiguous nature of thetreatment zones in the longitudinal direction L-L.

The arrangement and geometry of the electrode pads, as well as thearrangement and geometry of the tails of the flexible circuits may alsofacilitate folding or otherwise collapsing the balloon into a relativelycompact un-expanded state. For instance, in embodiments with an expandeddiameter of up to about 10 mm, the device in an un-expanded state mayhave as low as an about 1 mm diameter.

Some embodiments may utilize a standard electrode assembly havingidentical dimensions and construction, wherein the number and relativeposition of electrode assemblies on an outer surface of an expandablemember or a balloon becomes a function of the expandable member orballoon diameter and/or length while electrode assembly geometriesremain unchanged amongst various expandable member or balloon sizes. Therelative positioning of electrode assemblies relative to the expandablemember or balloon diameter and/or length may then be determined by thedesired degree or avoidance of circumferential and/or axial overlap ofadjacent electrode pads of neighboring electrode assemblies on anexpandable member or a balloon of a given size. In other embodiments,however, all of the electrode assemblies on the expandable member orballoon may not necessarily be identical.

The system 100 may be used to perform a method of treatment inaccordance with one non-limiting embodiment of the disclosure. Forexample, the control unit 110 may be operationally coupled to theablation device 120, which may be inserted into a body passageway suchthat an expandable member 130 (having a plurality of electrodeassemblies) may be placed adjacent to a first section of the bodypassageway where therapy is required. Placement of the ablation device120 at the first section of the body passageway where therapy isrequired may be performed according to conventional methods, e.g., overa guidewire under fluoroscopic guidance. Once inserted, the expandablemember 130 may be made to expand from a collapsed delivery configurationto an expanded configuration, for example by pressurizing fluid fromabout 2-10 atm in the case of a balloon. This may cause the electrodesand/or electrode assemblies of the expandable member 130 to come intocontact with the first section of the body passageway.

In some embodiments, the control unit 110 may measure impedance at theelectrode assemblies to confirm apposition of the electrodes with thebody passageway. In at least some of these embodiments, the treatmentmay proceed even if apposition is not sensed for all of the electrodes.For instance, in some embodiments, the treatment may proceed ifapposition is sensed for 50% or more of the electrodes, and may allowfor less than complete uniformity of apposition circumferentially and/oraxially. For example, in some instances the catheter may be positionedsuch that one or more of the proximal electrodes are in the aorta A andexposed to blood, and impedance sensed for such electrodes may not fallwithin a pre-designated range (such as, for example, 500-1600 ohms),indicating an absence of tissue apposition for those electrodes. In someinstances, the system may allow for user authorization to proceed withthe treatment even if there is less than uniform electrode/tissueapposition. Subsequently, the control unit 110 may activate theelectrodes to create a corresponding number of lesions. Duringactivation of the electrodes, the control unit 110 may use temperaturesensors of the electrode pads to monitor heat of the electrode and/orthe tissue. In this manner, more or less power may be supplied to eachelectrode pad as needed during treatment.

In some embodiments, the control unit 110 may apply a uniform standardfor determining apposition to all the electrodes of the ablation device120. For instance, the control unit 110 may utilize the samepre-designated range of resistance measurements to all of theelectrodes. In other instances, however, including some, although notall, monopolar applications, different standards may be applied todifferent monopolar electrodes for determining apposition. For example,in some monopolar embodiments, each monopolar electrode may define adiscrete electrical circuit through the tissue to the common/indifferentelectrode (or electrodes), and the characteristics of those circuits(e.g. resistance) may vary significantly based on the distance betweenthe monopolar electrode and common electrode, the tissue characteristicstherebetween, and other geometries and characteristics of the device andsurrounding tissue. As such, in at least some embodiments, it may bedesirable to apply criteria for determining apposition that variesdepending on, e.g., the distance between the monopolar electrode and acommon ground electrode (e.g. the greater the distance between the twoelectrodes, the higher the impedance measurement required to determinegood apposition). In other embodiments, however, the variance due tothese differences in distance and other geometries may be minimal ornon-substantive, and a uniform standard may be applied.

After the prescribed therapy in the first section of the body passagewayis complete, the expandable member 130 may then be collapsed and movedto an untreated second section of the body passageway where therapy isrequired to repeat the therapy applied in the first section of the bodypassageway, and similarly to other sections as needed. The sections maybe directly adjacent, or may be separated or spaced apart by somedistance.

In some instances, alternative methods will be utilized. For instance,in some embodiments, the treatment may be performed at only a singlelocation in the body passageway, and it may not be necessary to move theexpandable member to multiple locations in the body passageway.

Referring to an example of renal hypertension involving the reduction ofexcessive nerve activity, the system 100 may be used to effect anon-piercing, non-ablating way to direct energy to affect nerveactivity. Accordingly, the body passageway may be a renal arterysurrounded by nervous tissue. Electrodes on the expandable member 130may be powered to deliver energy in the known direction of a nerve to beaffected, the depth of energy penetration being a function of energydosage, electrode type (e.g. monopolar vs. bipolar) and electrodegeometry. U.S. Patent Application Publication No. 2008/0188912 entitled“System for Inducing Desirable Temperature Effects on Body Tissue”, thefull disclosure of which is incorporated herein by reference, describessome considerations for electrode geometry and the volume of tissuetreatment zones that may be taken into account in some, although notnecessarily all, embodiments. In some instances, empirical analysis maybe used to determine the impedance characteristics of nervous tissuesuch that the ablation device 120 may be used to first characterize andthen treat tissue in a targeted manner. The delivery and regulation ofenergy may further involve accumulated damage modeling, as well.

As shown, each lesion may be created in a corresponding treatment zoneA-D of the expandable member 130. Accordingly, any lesion made in oneparticular treatment A-D zone may not circumferentially overlap with alesion of an adjacent treatment zone A-D at any point along theoperational axis O-O. In some embodiments, a treatment zone of theexpandable member 130 may have more than one electrode pad, and thus insuch cases, lesions created by those electrode pads maycircumferentially overlap. In those cases, more lesions may be requiredfor a particular anatomy or a pair of electrode pads may be required forperforming a diagnostic routine before therapy is applied. Regardless,circumferential overlap of electrodes of adjacent treatment zones maynot be present.

Depending on the particular remodeling effect required, the control unitmay energize the electrodes with about 0.25 to about 5 Watts averagepower for about 1 to about 180 seconds, or with about 0.25 to about 900Joules. Higher energy treatments may be done at lower powers and longerdurations, such as 0.5 Watts for 90 seconds or 0.25 Watts for 180seconds. In monopolar embodiments, the control unit may energize theelectrodes with up to 30 Watts for up to 5 minutes, depending onelectrode configuration and distance between the electrodes and thecommon ground. A shorter distance may provide for lower energy for ashorter period of time because energy travels over more localized areawith fewer conductive losses. In an example embodiment for use in renaldenervation, energy may be delivered for about 30 seconds at a treatmentsetting of about 5 Watts, such that treatment zones may be heated toabout 68° C. during treatment. As stated above, power requirements maydepend heavily on electrode type and configuration. Generally, withwider electrode spacing, more power may be required, in which case theaverage power could be higher than 5 Watts, and the total energy couldexceed 45 Joules. Likewise, using a shorter or smaller electrode pairmay require scaling the average power down, and the total energy couldbe less than 4 Joules. The power and duration may be, in some instances,calibrated to be less than enough to cause severe damage, andparticularly less than enough to ablate diseased tissue within a bloodvessel. The mechanisms of ablating atherosclerotic material within ablood vessel have been well described, including by Slager et al. in anarticle entitled, “Vaporization of Atherosclerotic Plaque by SparkErosion” in J. of Amer. Cardiol. (June, 1985), on pp. 1382-6; and byStephen M. Fry in “Thermal and Disruptive Angioplasty: a Physician'sGuide”; Strategic Business Development, Inc., (1990), the fulldisclosure of which is incorporated herein by reference.

In some embodiments, energy treatments applied to one or both of thepatient's renal arteries may be applied at higher levels than would bepossible in other passageways of the body without deleterious effects.For instance, peripheral and coronary arteries of the body may besusceptible to a deleterious long-term occlusive response if subjectedto heating above a certain thermal response limit. It has beendiscovered that renal arteries, however, can be subjected to heatingabove such a thermal response limit without deleterious effect.

In some embodiments, the electrode(s) described herein may be energizedto assess and then selectively treat targeted tissue to achieve adesired therapeutic result by a remodeling of the treated tissue. Forexample, tissue signature may be used to identify tissue treatmentregions with the use of impedance measurements. Impedance measurementsutilizing circumferentially spaced electrodes within a body passage maybe used to analyze tissue. Impedance measurements between pairs ofadjacent electrodes may differ when the current path passes throughdiseased tissue, and when it passes through healthy tissues of a luminalwall, for example. Hence, impedance measurements between the electrodeson either side of diseased tissue may indicate a lesion or other type oftargeted tissue, while measurements between other pairs of adjacentelectrodes may indicate healthy tissue. Other characterization, such asintravascular ultrasound, optical coherence tomography, or the like, maybe used to identify regions to be treated either in conjunction with, oras an alternative to, impedance measurements. In some instances, it maybe desirable to obtain baseline measurements of the tissues to betreated to help differentiate adjacent tissues, as the tissue signaturesand/or signature profiles may differ from person to person.Additionally, the tissue signatures and/or signature profile curves maybe normalized to facilitate identification of the relevant slopes,offsets, and the like between different tissues. Impedance measurementsmay be achieved at one or more frequencies, ideally two differentfrequencies (low and high). Low frequency measurement may be done inrange of about 1-10 kHz, or about 4-5 kHz and high frequency measurementmay be done in range of about 300 kHz-1 MHz, or between about 750 kHz-1MHz. Lower frequency measurement mainly represents the resistivecomponent of impedance and may correlate closely with tissue temperaturewhere higher frequency measurement may represent the capacitivecomponent of impedance and may correlate with destruction and changes incell composition.

Phase angle shift between the resistive and capacitive components ofimpedance may also occur due to peak changes between current and voltageas result of capacitive and resistive changes of impedance. The phaseangle shift may also be monitored as means of assessing tissue contactand lesion formation during RF denervation.

In some embodiments, remodeling of a body lumen or passageway may beperformed by gentle heating in combination with gentle or standarddilation. For example, an angioplasty balloon catheter structure havingelectrodes disposed thereon may apply electrical potentials to thevessel wall before, during, and/or after dilation, optionally incombination with dilation pressures which are at or significantly lowerthan standard, unheated angioplasty dilation pressures. Where ballooninflation pressures of 10-16 atmospheres may, for example, beappropriate for standard angioplasty dilation of a particular lesion,modified dilation treatments combined with appropriate electricalpotentials (through flexible circuit electrodes on the balloon,electrodes deposited directly on the balloon structure, or the like)described herein may employ from about 10-16 atmospheres or may beeffected with pressures of about 6 atmospheres or less, and possibly aslow as about 1 to 2 atmospheres. Such moderate dilation pressures may(or may not) be combined with one or more aspects of the tissuecharacterization, tuned energy, eccentric treatments, and othertreatment aspects described herein for treatment of body lumens, thecirculatory system, and diseases of the peripheral vasculature.

In many embodiments, gentle heating energy added before, during, and/orafter dilation of a body passageway may increase dilation effectivenesswhile lowering complications. In some embodiments, such controlledheating with a balloon may exhibit a reduction in recoil, providing atleast some of the benefits of a stent-like expansion without thedisadvantages of an implant. Benefits of the heating may be enhanced(and/or complications inhibited) by limiting heating of the adventitiallayer below a deleterious response threshold. In many cases, suchheating of the intima and/or media may be provided using heating timesof less than about 10 seconds, often being less than 3 (or even 2)seconds. In other cases, very low power may be used for longerdurations. Efficient coupling of the energy to the target tissue bymatching the driving potential of the circuit to the target tissue phaseangle may enhance desirable heating efficiency, effectively maximizingthe area under the electrical power curve. The matching of the phaseangle need not be absolute, and while complete phase matching to acharacterized target tissue may have benefits, alternative systems maypre-set appropriate potentials to substantially match typical targettissues; though the actual phase angles may not be matched precisely,heating localization within the target tissues may be significantlybetter than using a standard power form.

In some embodiments, monopolar (unipolar) RF energy application may bedelivered between any of the electrodes on the expandable member and acommon ground or return electrode positioned on the outside skin or onthe device itself. Monoploar RF may be desirable in areas where deeplesions are required. For example, in a monopolar application, eachelectrode pair may be powered with positive polarity rather than havingone positive pole and one negative pole per pair. In some embodiments, acombination of monopolar and bipolar RF energy application may be donewhere lesions of various depth/size can be selectively achieved byvarying the polarity of the electrodes of the pair.

The application of RF energy may be controlled so as to limit atemperature of target and/or collateral tissues, for example, limitingthe heating of target tissue such that neither the target tissue nor thecollateral tissue sustains irreversible thermal damage. In someembodiments, the surface temperature range may be from about 50° C. toabout 90° C. For gentle heating, the surface temperature may range fromabout 50° C. to about 70° C., while for more aggressive heating, thesurface temperature may range from about 70° C. to about 90° C. Limitingheating so as to inhibit heating of collateral tissues to less than asurface temperature in a range from about 50° C. to about 70° C., suchthat the bulk tissue temperature remains mostly below about 50° C. toabout 55° C., may inhibit an immune response that might otherwise leadto stenosis, thermal damage, or the like. Relatively mild surfacetemperatures between about 50° C. and about 70° C. may be sufficient todenature and break protein bonds during treatment, immediately aftertreatment, and/or more than one hour, more than one day, more than oneweek, or even more than one month after the treatment through a healingresponse of the tissue to the treatment so as to provide a bigger vessellumen and improved blood flow.

In some embodiments, the target temperature may vary during thetreatment, and may be, for instance, a function of treatment time. Onepossible target temperature profile may include a treatment with aduration of 30 seconds and a twelve second ramp up from nominal bodytemperature to a maximum target temperature of about 68° C. During thetwelve second ramp up phase, the target temperature profile may bedefined by a quadratic equation in which target temperature (T) is afunction of time (t). The coefficients of the equation may be set suchthat the ramp from nominal body temperature to about 68° C. may follow apath analogous to the trajectory of a projectile reaching the maximumheight of its arc of travel under the influence of gravity. In otherwords, the ramp may be set such that there may be a constantdeceleration in the ramp of temperature (d²T/dt²) and a linearlydecreasing slope (dT/dt) in the temperature increase as 12 seconds and68° C. are reached. Such a profile, with its gradual decrease in slopeas it approaches 68° C., may facilitate minimizing over and/orundershoot of the set target temperature for the remainder of thetreatment. In some embodiments, the target temperature profile may beequally suitable for bipolar or monopolar treatments, although, in atleast some monopolar embodiments, treatment time may be increased. Othertarget temperature profiles utilizing different durations of time (i.e.,3 seconds, 5 seconds, 8 seconds, 12 seconds, 17 seconds, etc.) and settarget temperatures (55° C., 60° C., 65° C., 70° C., 75° C., etc.) invarious combinations may be used as desired. For each of the targettemperature profiles considered, a temperature ramp embodying orapproximating a quadratic equation may be utilized, however, anyfunction or other profile that efficiently heats tissue, optimizestreatment time, and avoids thermal damage to target tissue may be used.However, in still other embodiments, it will not be necessary to utilizea temperature profile that achieves all of these goals. For instance andwithout limitation, in at least some embodiments, optimization oftreatment time may not be essential.

A control method may be executed using the processing functionality ofthe control unit 110 of FIG. 1 and/or control software, described infurther detail above, or in other manners. In at least some instances,the control method may provide for fine regulation of temperature orother treatment parameter(s) at the various treatment sites of thedevice, while utilizing a relatively simple and robust energy generatorto simultaneously energize several of the electrodes or other deliverysites at a single output setting (e.g. voltage), which may minimizecost, size and complexity of the system. The control method may minimizedeviation from target temperature or other treatment parameter(s), andhence minimize variation in demand on the energy generator (e.g. voltagedemand) during any time slice of the treatment.

In some embodiments, it may be desirable to regulate the application ofRF or other energy based on target temperature profiles such as thosedescribed above to provide for a gentle, controlled, heating that avoidsapplication of high instantaneous power and, at a microscopic level,associated tissue searing or other damage, which could undesirablyresult in heat block or otherwise cause a net reduction in thermalconduction heat transfer at the device/tissue interface. In other words,by avoiding higher swings in temperature and the resultant heavierinstantaneous application of energy to reestablish temperature near thetarget temperature, tissue integrity at the immediate interface locationmay be preserved. Tissue desiccation may result in a net loss of thermalconductivity, resulting in reduced effective transfer of gentle,therapeutic delivery of energy to target tissues beyond theelectrode/tissue interface.

Those of skill in the art will appreciate that although a particularcontrol method may be presented for purposes of illustration in thecontext of the particular electrosurgical devices already describedabove, that these control methods and similar methods could bebeneficially applied to other electro-surgical devices.

In general, the control method may seek to maintain the varioustreatment sites at a pre-defined target temperature, such as at one ofthe target temperature profiles discussed above. In some embodiments,the control method may maintain the treatment site(s) at the pre-definedtarget temperature primarily by regulating output voltage of the RFgenerator and determining which of the electrodes will by energized at agiven time slice (e.g. by switching particular electrodes on or off forthat cycle).

The output setting of the generator and switching of the electrodes maybe determined by a feedback loop that takes into account measuredtemperature as well as previous desired output settings. During aparticular treatment cycle (e.g. a 25 millisecond slice of thetreatment), each of the electrodes may be identified for one of threestates: off, energized, or measuring. In some embodiments, electrodesmay only be in energized and/or measuring states (an electrode that isenergized may also be measuring) if they meet certain criteria, with thedefault electrode state being off. Electrodes that have been identifiedas energized or measuring electrodes may have voltage applied or bedetecting temperature signals for a portion of the cycle, or for theentire cycle.

In some embodiments, the control method may be designed to keep as manycandidate electrodes as possible as close to target temperature aspossible while minimizing variations in temperature and hence minimizingvariations in voltage demand from treatment cycle to treatment cycle.

Each electrode may be initially set to off. At a next step, one of theelectrodes may be designated as a primary electrode for that treatmentcycle. As discussed in further detail below, during the treatment, theprimary electrode designated may vary from treatment cycle to treatmentcycle (e.g. cycle through all of the available electrodes). Thedetermination of which electrode may be designated as the primaryelectrode may be done by accessing a look-up table or using any othersuitable functionality for identifying a primary electrode and varyingthe choice of primary electrode from treatment cycle to treatment cycle.

Additionally, at the next step discussed above, additional electrodesmay also be designated as candidate electrodes for energization and/ormeasuring during that treatment cycle. The additional electrodesdesignated may be candidates by virtue of being in a certainrelationship or lacking a certain relationship relative to thedesignated primary electrode for that treatment cycle.

For instance, in some bipolar electrode embodiments, some of theelectrodes on the ablation device may be arranged in a manner such thatthere may be a potential for current leakage between the primaryelectrode and those other electrodes if both the primary electrode andthose additional electrodes are energized simultaneously in a treatmentcycle, which may undesirably cause interference with the temperaturemeasurement by the associated temperature sensor, imprecision in theamount of energy delivered at each electrode, or other undesirableconsequences. For instance, in the embodiment illustrated in FIG. 3, ifelectrode pad 150 c is designated as a primary electrode, electrode pads150 d and 170 d, which have negative poles immediately adjacent orproximate the positive pole of electrode pad 150 c, may be considered tobe not candidates for measuring and/or energization for that particulartreatment cycle, since they are leakage-inducingly proximate to thedesignated primary electrode. Additionally, in this embodiment,electrode pad 150 b, which may have a positive pole immediately adjacentor proximate the negative pole of electrode pad 150 c, may be consideredto not be a candidate, since it may also be leakage-inducingly proximateto the designated primary electrode. Furthermore, in this particularembodiment, electrode pad 170 b may also be considered a non-candidatebecause it may be on the same flex structure as the leakage-inducinglyproximate electrode pad 150 b. Finally, in this particular embodiment,electrode pads 150 a and 170 a may be considered candidates because theyare adjacent non-candidates.

As another non-limiting example, in some monopolar electrodeembodiments, the candidate electrodes may be the monopolar electrodesthat have similar measured or estimated electrical circuit properties toone or more measured or estimated properties of the electrical circuitassociated with the primary electrode. In other words, in some monopolarsystems, it may be desirable to only simultaneously energize monopolarelectrodes that define substantially similar electrical circuits to theelectrical circuit defined by the primary monopolar electrode (e.g. thecircuit defined by the monopolar electrode, the common electrode, and apathway through the patient's tissue). In some instances, this mayfacilitate uniformity in current flow during energization. In otherembodiments, a pre-defined table or other listing or association maydetermine which electrodes are candidate electrodes based on the currentprimary electrode.

In at least some embodiments, switches associated with non-candidatesmay be opened to isolate the non-candidates from the rest of thesystem's circuitry. This switching, in at least some embodiments, mayalso or alternatively be used to otherwise maximize the number ofavailable electrode pairs available for energization provided that acommon ground between pairs is not affected by the switching off.

In other embodiments, the ablation device may be configured to avoid thepotential for leakage or otherwise take such leakage into account, and,accordingly, all the electrodes of the device may be candidates forenergization and/or measuring during a treatment cycle.

In some embodiments, the assignment of an electrode as either theprimary electrode, candidate, or non-candidate may be determined by asequence matrix or look up table in an array that identifies the statusof each of the electrodes and an order for the designation of primaryelectrodes. In one non-limiting embodiment, the primary electrodedesignation cycles circumferentially through the proximate electrodesand then circumferentially through the distal electrodes (e.g. in FIG.3, the sequence may be 170 a, b, c, d, 150 a, b, c, d). However, anypattern or other methodology could be used including ones that optimizedistance between the next in sequence, the nearness of next in sequence,or the evenness of distribution.

In some embodiments, additional conditions may result in a particularelectrode being set to off for a particular treatment cycle and/or forthe remainder of the treatment. For instance, as discussed below, duringthe course of treatment, as much as 4° C. temperature overshoot may beallowed (e.g., even if such overshoot results in the electrode not beingenergized, it may not necessarily be set to off and may still beavailable for measuring); however, in at least some embodiments, ifeight consecutive treatment cycles measure temperature overshoot for aparticular electrode, that electrode may be set to off for the remainderof the treatment, with the treatment otherwise continuing and withoutotherwise changing the control loop process discussed below.

At a next step, target voltages for each of the primary and othercandidate electrodes may be determined. In some embodiments, a targetvoltage for a particular electrode may be determined based on atemperature error associated with the treatment site of that electrodeas well as the last target voltage calculated (although not necessarilyapplied) for that electrode. Temperature error may be calculated bymeasuring the current temperature at the treatment site (e.g. utilizingthe temperature sensor associated with the electrode proximate thattreatment site) and determining the difference between the measuredtemperature and the target temperature for that instant of time in thetreatment.

Those of skill in the art will appreciate that while some embodimentsare described as using voltage as a control variable, power could beused as an alternative to voltage for the control variable, based on,for instance, a known relationship between power and voltage (i.e. powerequaling voltage times current or impedance).

One embodiment may include a sub-routine for determining a targetvoltage for an electrode. For example, one step may include calculatinga temperature error from target (T_(e)) by subtracting the targettemperature at that time (T_(g)) from the actual temperature (T) (e.g.as measured by a thermistor associated with that electrode).Subsequently, it may be determined whether the temperature errorcalculated at the calculating step is greater than 4° C. (i.e. if thetarget temperature is 68° C., determining if the temperature as measuredby the thermistor is above 72° C.). If the temperature error is greaterthan 4° C., the sub-routine may assign that electrode a target voltageof zero for that treatment cycle. If the temperature error is notgreater than 4° C., the subroutine may proceed to a next step anddetermine whether the temperature error is greater than 2° C. If thetemperature error is greater than 2° C., the sub-routine may assign thatelectrode a target voltage of 75% (or another percentage) of the lastassigned target voltage for that electrode. If the temperature error isnot greater than 2° C., the sub-routine may assign a target voltage forthat electrode based on the equation:V=K _(L) V _(L) +K _(P) T _(e) +K _(I)∫^(t) _(t-n sec) T _(e AVE)

-   -   where:        -   V is the target voltage;        -   T_(e) is a temperature error from target;        -   V_(L) is the last assigned electrode voltage;        -   K_(L), K_(P), and K_(I) are constants; and        -   n is a time value ranging from 0 to t seconds.

In some embodiments, the equation used may be:

V = 0.75  V_(L) + K_(p)T_(e) + K_(I)∫_(t − n  sec )^(t)T_(e  AVE) 

-   -   where:        -   V is the target voltage;        -   T_(e) is the temperature error from target;        -   V_(L) is the last assigned electrode voltage;        -   K_(P) is a constant from proportionate control; and        -   K_(I) is a constant from integral control.

In some embodiments, it may be beneficial to use only the last assignedelectrode voltage for determining a target voltage, rather thanutilizing averages of voltages or voltages from earlier treatmentcycles, as, in some cases, use of earlier voltages may be a source forcomputational error in embodiments that focus on fine control of thetarget temperature.

Once target voltages are determined for the primary electrode and othercandidate electrodes, it may be determined whether the target voltagefor the primary electrode is greater than zero. If not, the outputvoltage of the RF generator may be set for that treatment cycle to thelowest target voltage determined for the other candidate electrodes. Ifthe target voltage determined for the primary electrode is greater thanzero, the output voltage of the RF generator may be set for thattreatment cycle to the target voltage of the primary electrode.

Next, the primary and other candidate electrodes with a target voltagegreater than zero may be identified as electrodes to be energized. Inalternative embodiments, candidate electrodes other than the primary mayonly be energized if the target voltages determined for those electrodesis 6V greater than the set voltage. In some embodiments, candidateelectrodes other than the primary may only be energized if the targetvoltages determined for these electrodes are 1, 5 or 10V greater thanthe set voltage.

Lastly, it may be determined whether the electrodes to be energized arecurrently at temperatures greater than 68° C. Those electrodes that areat temperatures greater than 68° C. may be switched off or otherwiseprevented from being energized in that treatment cycle, and thoseelectrodes otherwise meeting the above criteria may be energized at theset voltage. Subsequently, another treatment cycle begins, and thecontrol method may be repeated until the treatment is complete. In someembodiments, each treatment cycle will be non-overlapping with theprevious and next cycles (e.g. the steps of the control method will becompletely performed before the next cycle's steps begin), although, inother embodiments, the cycles may be overlapping at least to someextent.

Turning now to FIG. 7, a renal nerve ablation device 300 may include anexpandable member 130 that may be disposed at, on, about, or near adistal region of the elongate tubular member or catheter shaft 122, asdiscussed above. In some embodiments, the proximal waist 136 of theexpandable member 130 may be fixedly attached to the elongate tubularmember or catheter shaft 122. In some embodiments, the renal nerveablation device 300 includes a ride-along electrode support 305 with oneor more electrodes. In some embodiments, the electrode support 305 maybe fixedly attached to the elongate tubular member or catheter shaft122. The electrode support 305 may be free from attachment to the body135 of the expandable member 130. In some embodiments, the electrodesupport 305 may be expandable from a collapsed delivery state to anexpanded state, such as a basket or a plurality of struts or elongatemembers, for example. The electrode support 305 may include one or moreflexible elongate members 310 each having a proximal end 320 which maybe fixedly attached to the catheter shaft 122. In some embodiments, aplurality of elongate members 310 have proximal ends 320 fixedlyattached to the catheter shaft 122. In some embodiments, the distal ends315 of the elongate members 310 are free of any attachment to thecatheter shaft 122 and expandable member 130. In other embodiments, thedistal ends 315 may be connected to each other, as shown in FIG. 7,and/or to a connection member or ring (not shown). In some embodiments,elongate members 310 are free from attachment to the catheter shaft 122or to the expandable member 130 at least from a point distal of theproximal ends 320 and extending to the distal ends 315. The elongatemembers 310 may be connected to the catheter shaft 122 and unconnectedto the expandable member 130. In some embodiments, proximal ends 320 ofthe elongate members 310 may be attached to the proximal waist 136 ofthe expandable member 130 in a region of connection between the proximalwaist 136 and the catheter shaft 122.

In some embodiments, the electrode support 305 is a separate elementfrom the expandable member 130 and is unconnected to the expandablemember 130. As shown in FIG. 8, the electrode support 305 may be fixedlyconnected to a separate elongate element or catheter shaft 322. In someembodiments, the electrode support 305 may be deliverable separatelyfrom the expandable member 130. In this embodiment, the electrodesupport 305 may be delivered to a body lumen, followed by delivery ofthe expandable member 130 through catheter 322. Once the expandablemember 130 is positioned within the electrode support 305, theexpandable member 130 is expanded thereby expanding the electrodesupport 305 and placing the electrode assemblies 325 on the electrodesupport 305 in contact with the interior of the body lumen. Followingtreatment with the electrode assemblies 325, the expandable member 130may be contracted. The lack of attachment between the electrode support305 and the majority of the expandable member 130 allows the expandablemember 130 to be deflated in any manner. For example, the expandablemember 130 may be deflated via a vacuum source, re-folded or twisted byapplying torque to at least a portion of the expandable member 130, orby being withdrawn back into a guide catheter 14. The contracted ordeflated expandable member 130 may be withdrawn first followed bywithdrawal of the electrode support 305. Alternatively, the contractedexpandable member 130 and the electrode support 305 may be removedsimultaneously. The separate electrode support 305 does not interferewith deflation, contraction, twisting, or re-folding of the expandablemember 130. The elongate members 310 collapse into their pre-expansionstate for withdrawal into a guide catheter 14.

In some embodiments, the electrode support 305 is disposed over theexpandable member 130 and expands when the expandable member 130 isexpanded. The elongate members 310 are not attached to the expandablemember 130 and during expansion the elongate members 310 move fartherapart from each other. In some embodiments, the electrode support 305may be used with a variety of sizes of expandable member 130. Theelongate members 310 move farther apart as the diameter of theexpandable member 130 increases. Expansion of the expandable member 130within a body lumen forces the elongate members into contact with theinner walls of the body lumen. Upon contraction of the expandable member130, the electrode support 305 may remain in substantially the expandedconfiguration, allowing the expandable member 130 to contract, twist,fold, or otherwise attain a configuration suitable for retraction into adelivery sheath or catheter. The unattached electrode support 305 doesnot interfere with expansion and contraction of the expandable member.In some embodiments, the electrode support 305 collapses or folds ontothe previously folded or collapsed expandable member 130 as the entireablation device 300 is retracted into a delivery sheath or catheter whenthe catheter 122 is withdraw proximally. In other embodiments, theexpandable member and electrode support 305 are withdrawn in order tocollapse both elements substantially simultaneously. In otherembodiments, the electrode support 305 may be biased in a collapsedconfiguration, such that when the expandable member 130 is contracted,the electrode support 305 automatically returns to a contractedconfiguration.

The electrode support 305 may include a plurality of electrodeassemblies 325. In some embodiments, each elongate member 310 maycontain one or more electrode assemblies 325. In some embodiments, eachelectrode assembly 325 may include a ground electrode 330, an activeelectrode 335, and a sensor element 340. In some embodiments, eachelongate member 310 may have electrode assemblies 325 that extend fromalternating sides, as shown in FIG. 7. In some embodiments, theelectrodes and sensors of each electrode assembly 325 may be arranged asshown in FIG. 4. In some embodiments, the electrode support 305 may bemade up of one or more elongate members 310 extending generally parallelto the longitudinal axis of the expandable member 130, as shown in FIG.7. In other embodiments, the elongate members 310 may be twisted orcanted at an angle from the longitudinal axis.

In some embodiments, the expandable member 132 has one or more channels134 extending along a length of the expandable member 132. The channels134 are configured to remain when the expandable member 132 is expanded.When the expandable member 132 is placed within a body lumen such as ablood vessel, and expanded, the channels 134 allow partial fluid flowacross the expandable member 132. The channels 134 may be substantiallyparallel to a longitudinal axis of the expandable member 132, or thechannels may be arranged in other configurations. In the embodimentillustrated in FIGS. 9-11, an expandable member 132 has three channels134 extending in a spiral along the expandable member 132. Any number ofchannels 134 may be included in the expandable member 132. The channels134 may be spaced apart in a manner that allows for the elongate members360 of the electrode support 355 to be disposed between channels 134. Insome embodiments, the elongate members 360 extend in a spiral matchingthe angle of the channels 134.

Turning now to FIG. 12, in some embodiments, a renal nerve ablationdevice 400 may include a ride-along electrode support 405 in which aplurality of flexible elongate members 410 extend around an expandablemember 130 at an angle with respect to the longitudinal axis. Asdiscussed above, the expandable member 130 may be disposed at, on,about, or near a distal end of the elongate tubular member or cathetershaft 122. In some embodiments, the electrode support 405 may be fixedlyattached to the elongate tubular member or catheter shaft 122, and freefrom attachment to the body 135 of the expandable member 130. In someembodiments, the electrode support 405 may be expandable from acollapsed delivery state to an expanded state. The electrode support 405may include one or more electrode assemblies 425. The electrode assembly425 may include a plurality of flexible elongate members 410 withproximal ends 420 fixedly attached to the catheter shaft 122. In theembodiment illustrated in FIG. 12, the electrode assembly 425 has threeelongate members 410 connected to each other only at their proximal ends420. The distal ends 415 of the elongate members 410 may be free of anyattachment to each other and to the expandable member 130. In someembodiments, proximal ends 420 of the elongate members 410 may beattached to the proximal waist 136 of the expandable member 130 in aregion of connection between the proximal waist 136 and the cathetershaft 122.

In some embodiments, the electrode support 405 is disposed over theexpandable member 130 and expands when the expandable member 130 isexpanded. The elongate members 410 are not attached to the expandablemember 130 and during expansion the elongate members 410 move fartherapart from each other. The electrode support 405 may include a pluralityof electrode assemblies 425. In some embodiments, each electrodeassembly 425 includes a plurality of elongate members 410.

In some embodiments, each electrode assembly 425 may include threeelongate members 410. A first elongate member 410 may carry a pluralityof ground electrodes 430, a second elongate member 410 may carry aplurality of active electrodes 435, and a third elongate member 410 maycarry a plurality of sensor elements 440. In some embodiments, theground electrodes 430, active electrodes 435, and sensor elements 440are grouped longitudinally on adjacent elongate members 410. In someembodiments, a single sensor element 440 may be disposed on an elongatemember 410 between a first elongate member 410 with a plurality ofground electrodes 430 and a second elongate member 410 with a pluralityof active electrodes 435. In some embodiments, such as that illustratedin FIG. 12, the elongate members 410 may be twisted or canted at anangle from the longitudinal axis. In some embodiments, the electrodesupport 405 includes two electrode assemblies 425, positioned onsubstantially opposite sides of the expandable member 130. In otherembodiments, the electrode support 405 includes three electrodeassemblies 425 positioned at substantially equal distances from eachother around the expandable member 130. In some embodiments, theelongate members 410 are substantially parallel.

In some embodiments, the axial position of groups of ground 430 andactive 435 electrodes and sensor elements 440 are offset on adjacentelectrode assemblies 425. For example, as shown in FIG. 12, in someembodiments, the electrode assemblies may be arranged on the expandablemember 130, shown here in an expanded state, according to a pair ofgenerally cylindrical treatment zones A and B. In other embodiments, theexpandable member 130 or other components of the treatment system mayinclude additional electrode assemblies that are not in a treatment zoneor are otherwise not used or configured to deliver a treatment energy.

The treatment zones A and B and associated electrode assemblies 425 a-care further illustrated in FIG. 13, which is an “unrolled” depiction ofa portion of the electrode support 405 of FIG. 12. The treatment zones Aand B may be longitudinally adjacent to one another along longitudinalaxis L-L, and may be configured such that energy applied by theelectrode assemblies create treatments that do not overlap. Treatmentsapplied by the longitudinally adjacent bipolar electrode assemblies 425a-c may be circumferentially non-continuous along longitudinal axis L-L.For example, with reference to FIG. 13, lesions created in treatmentzone A may in some embodiments minimize overlap about a circumference(laterally with respect to L-L in this view) with lesions created intreatment zone B. In other embodiments, however, the energy applied bythe electrode assemblies, such as the electrode assemblies shown in FIG.13, may overlap, longitudinally, circumferentially, and/or in otherways, to at least some extent.

In some embodiments, the sensor element 440 may be disposed adjacent tothe ground electrode 430 and/or the active electrode 435. In someembodiments, the ground electrode 430, the active electrode 435, and/orthe sensor element 440 may extend along a length of the expandablemember 130. In some embodiments, the ground electrode 430, the activeelectrode 435, and/or the sensor element 440 may extend alongsubstantially a full length of the expandable member 130.

Turning to FIG. 14, in some embodiments, a renal nerve ablation device500 may include a ride-along electrode support 505 in which a pluralityof flexible elongate members 510 are disposed in a helical or spiralpattern or orientation along an outer surface of the expandable member130. As discussed above, the expandable member 130 may be disposed at,on, about, or near a distal end of the elongate tubular member orcatheter shaft 122. In some embodiments, the electrode support 505 maybe fixedly attached to the elongate tubular member or catheter shaft 122and free from attachment to the body 135 of the expandable member 130.In some embodiments, the electrode support 505 may be expandable from acollapsed delivery state to an expanded state. The electrode support 505may include an electrode assembly 525 which may include a plurality offlexible elongate members 510 with proximal ends 520 fixedly attached tothe catheter shaft 122. In the embodiment illustrated in FIG. 14, theelectrode assembly 525 has three elongate members 510 connected to eachother only at their proximal ends 520 and distal ends 515. In someembodiments, proximal ends 520 of the elongate members 510 may beattached to the proximal waist 136 of the expandable member 130 in aregion of connection between the proximal waist 136 and the cathetershaft 122.

In some embodiments, the electrode support 505 is disposed over theexpandable member 130 and expands when the expandable member 130 isexpanded. The elongate members 510 are free from attachment to the body135 of the expandable member 130 and are free from attachment to eachother except at their distal 515 and proximal ends 520, allowing theelongate members 510 to move farther apart from each other duringexpansion. The electrode support 505 may be used in combination withexpandable members 130 of varying expanded sizes. The elongate members510 may be attached to each other at their distal 515 and proximal 520ends. In some embodiments, the distal ends 515 of the elongate members510 may be attached to the distal waist 137 of the expandable member 130and the proximal ends 520 of the elongate members 510 may be attached toproximal waist 136 of the expandable member 130. In other embodiments,the distal 515 and proximal 520 ends of the elongate members 510 may beattached to the catheter shaft 122. The electrode support 505 mayinclude a plurality of electrode assemblies 525 spaced apart axiallyalong the electrode support 505.

In some embodiments, the electrode assembly 525 may include threeelongate members 510. A first elongate member 510 may carry a pluralityof ground electrodes 530, a second elongate member 510 may carry aplurality of active electrodes 535, and a third elongate member 510 maycarry a plurality of sensor elements 540. In some embodiments, theground electrodes 530, active electrodes 535, and sensor elements 540are grouped axially on adjacent elongate members 510, as illustrated inFIG. 14. In some embodiments, a single sensor element 540 may bedisposed on an elongate member 510 between a first elongate member 510with a plurality of ground electrodes 530 and a second elongate member510 with a plurality of active electrodes 535. In some embodiments, suchas that illustrated in FIG. 14, the elongate members 510 may be twistedor canted at an angle from the longitudinal axis, forming a helix. Insome embodiments, the electrode support 505 includes one or moreelongate support 511 disposed in a helical or spiral pattern ororientation along an outer surface of the expandable member 130. Theelongate supports 511 may balance the electrode assembly 525. Theelongate supports 511 may be free of electrodes or other elements. Insome embodiments, two sets of three elongate supports 511 may bepresent. The elongate supports 511 may be connected to each other onlyat their proximal and distal ends and may be free of attachment to thebody 135 of the expandable member 130. The distal ends 515 of theelongate members 510 may be connected to distal ends of the elongatesupports 511.

In some embodiments, the electrode support 505 includes circuitry (notshown) connected to the ground electrodes 530, active electrodes 535,and sensor elements 540. In some embodiments, the circuitry extends fromeach electrode proximally to the catheter shaft 122. In someembodiments, a first portion of the circuitry extends proximally alongthe elongate members 510 to the catheter shaft 122, and a second portionof the circuitry extends distally along the elongate members 510 to thedistal ends 515 of the elongate members 510. The second portion of thecircuitry may then be shifted to one or more of the elongate supports511 and extend proximally along the one or more elongate supports 511 tothe catheter shaft 122. Such a split distribution of the circuitry mayallow for narrower and more flexible elongate members 510.

The ground electrode 530, the active electrode 535, and the sensorelement 540 may be oriented generally parallel to each other. Thehelical or spiral pattern or orientation may be arranged such that aplane placed normal or perpendicular to the longitudinal axis L-L of theexpandable member 130 may intersect the electrode assembly 525, theground electrode 530, the active electrode 535, and/or the sensorelement 540 at a single location such that at no location along thelength of the expandable member 130 does the electrode assembly 525, theground electrode 530, the active electrode 535, and/or the sensorelement 540 overlap itself longitudinally. Other arrangements, however,are contemplated.

The helical orientation along the length of the expandable member 130forms at least one complete (360 degree) circumferential loop within thelumen or vessel that the expandable member 130 is positioned. Theelectrodes provide heating at a location within the tissue surroundingthe body passageway without damaging the wall of the body passageway inorder to disrupt the nerves located in the tissue surrounding the bodypassageway wall. A helical orientation is desirable to help avoid anincreased risk of stenosis that may be present when electrodes aredisposed within a single plane normal to a longitudinal axis of the bodypassageway (i.e., a circular electrode or group of electrodes).

In some embodiments, the renal nerve ablation device 300, 400, 500 mayinclude a single ground electrode 330, 430, 530 and a single activeelectrode 335, 435, 535. Accordingly, the ground electrode 330, 430, 530and the active electrode 335, 435, 535 may combine to form a bipolarelectrode pair. When the renal nerve ablation device 300, 400, 500 isenergized, such as in the manner(s) described above, RF energy or othersuitable energy may pass from the active electrode 335, 435, 535 to theground electrode 330, 430, 530, thereby creating a corresponding lesionor lesions along a body passageway within which the expandable member130 has been positioned. The sensor element 340, 440, 540 may bepositioned between the ground electrode 330, 430, 530 and the activeelectrode 335, 435, 535. The sensor element 340, 440, 540 may include atleast one temperature sensor, such as a thermistor or thermocouple,positioned on the outer surface of the expandable member 130. The atleast one temperature sensor may be positioned between the groundelectrode 330, 430, 530 and the active electrode 335, 435, 535, and maybe configured to monitor the temperature of the target tissue, theactive and ground electrodes, or both, as discussed above. In someembodiments, the at least one temperature sensor may include a pluralityof temperature sensors configured to monitor the temperature of thetarget tissue, the active electrodes, the ground electrodes, or anycombination thereof, at a plurality of locations along the length of theexpandable member 130.

Turning now to FIG. 15, in some embodiments, a renal nerve ablationdevice 600 may include an electrode support 605 similar to thatdiscussed above with regard to the embodiment of FIG. 14, but in whichthe electrode assembly 625 may lack a ground electrode, or the groundelectrode may not be connected to the control unit 110, such that theactive electrode 635 may form a monopolar electrode. As discussed above,the electrode support 605 may include a plurality of flexible elongatemembers 610 disposed in a helical or spiral pattern or orientation alongan outer surface of the expandable member 130. In some embodiments, theelectrode support 605 may be fixedly attached to the elongate tubularmember or catheter shaft 122. In some embodiments, the electrode support605 may be expandable from a collapsed delivery state to an expandedstate. The electrode support 605 may include an electrode assembly 625which may include a plurality of flexible elongate members 610 withproximal ends 620 fixedly attached to the catheter shaft 122. In theembodiment illustrated in FIG. 15, the electrode assembly 625 has threeelongate members 610 connected to each other only at their proximal ends620 and distal ends 615. In some embodiments, proximal ends 620 of theelongate members 610 may be attached to the proximal waist 136 of theexpandable member 130 in a region of connection between the proximalwaist 136 and the catheter shaft 122.

In some embodiments, the electrode support 605 is disposed over theexpandable member 130 and expands when the expandable member 130 isexpanded. The elongate members 610 are free from attachment to the body135 of the expandable member 130, allowing the elongate members 610 tomove farther apart from each other during expansion. The elongatemembers 610 may be attached to each other at their distal 615 andproximal 620 ends. In some embodiments, the distal ends 615 of theelongate members 610 may be attached to the distal waist 137 of theexpandable member 130 and the proximal ends 620 of the elongate members610 may be attached to proximal waist 136 of the expandable member 130.In other embodiments, the distal 615 and proximal 620 ends of theelongate members 610 may be attached to the catheter shaft 122. Theelectrode support 605 may include a plurality of electrode assemblies625 spaced apart axially along the electrode support 605.

In some embodiments, the electrode support 605 includes one or moreadditional elongate members 611 disposed in a helical or spiral patternor orientation along an outer surface of the expandable member 130. Theadditional elongate members 611 may balance the electrode assembly 625.The additional elongate members 611 may be free of electrodes or otherelements. In some embodiments, two sets of three additional elongatemembers 611 may be present. The additional elongate members 611 may beconnected to each other only at their proximal and distal ends and maybe free of connection to the body 135 of the expandable member 130.

In embodiments utilizing a monopolar electrode, a separate common groundelectrode 632 may be used. The common ground electrode 632 may becapable of being a return electrical pathway for the active electrode635. Thus, energy may be delivered to the active electrode 635 and thecommon ground electrode may be the return electrical pathway. As thename suggests, the common ground electrode may be utilized as a commonground for more than one active electrode. For example, the ablationdevice 600 may include a plurality of active electrodes, such as in FIG.15, and a common ground electrode may be a common ground for at leastsome or, in at least some embodiments, all of the active electrodes.Various embodiments are contemplated that include any suitable number ofactive electrodes including one, two, three, four, five, six, seven,eight, nine, ten, or more active electrodes.

Because the common ground electrode may be utilized as the returnelectrode for a plurality of active electrodes, the active electrodesneed not have a bipolar return electrode (i.e., ground trace) pairedwith each active electrode. This may allow active electrodes and/or theother structures associated therewith to be constructed with a smallersize or footprint. This may desirably impact the overall construction ofdevice. For example, smaller active electrodes may be more flexible,allow for easier contracting or folding of the electrode support whenproximally retracting the ablation device, reduce the profile of theablation device, or the like.

In use, the ablation device 300, 400, 500, 600 may be advanced through ablood vessel to a position adjacent to a target tissue (e.g., within arenal artery). In some embodiments, the target tissue may be one or morerenal nerves disposed about the renal artery. When suitably positioned,expandable member 130 may be expanded from a collapsed deliveryconfiguration to an expanded configuration. This may place the activeelectrode 335, 435, 535, 635 against the wall of the blood vessel. Theactive electrode 335, 435, 535, 635 may be activated. Ablation energymay be transmitted from the active electrode 335, 435, 535, 635, throughthe target tissue (where renal nerves may be ablated, modulated, orotherwise impacted), and back through the ground electrode 330, 430,530, 630, in a bipolar configuration, or back through the common groundelectrode 632, in a monopolar configuration.

The materials that can be used for the various components of theablation device 300, 400, 500, 600 (and/or other devices disclosedherein) may include those commonly associated with medical devices. Forsimplicity purposes, the following discussion makes reference to theablation device 300, 400, 500, 600. However, this is not intended tolimit the devices and methods described herein, as the discussion may beapplied to other similar tubular members and/or expandable membersand/or components of tubular members and/or expandable members disclosedherein.

The ablation device 300, 400, 500, 600 and the various componentsthereof may be made from a metal, metal alloy, polymer (some examples ofwhich are disclosed below), a metal-polymer composite, ceramics,combinations thereof, and the like, or other suitable material. Someexamples of suitable polymers may include polytetrafluoroethylene(PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylenepropylene (FEP), polyoxymethylene (POM, for example, DELRIN® availablefrom DuPont), polyether block ester, polyurethane (for example,Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC),polyether-ester (for example, ARNITEL® available from DSM EngineeringPlastics), ether or ester based copolymers (for example,butylene/poly(alkylene ether) phthalate and/or other polyesterelastomers such as HYTREL® available from DuPont), polyamide (forexample, DURETHAN® available from Bayer or CRISTAMID® available from ElfAtochem), elastomeric polyamides, block polyamide/ethers, polyetherblock amide (PEBA, for example available under the trade name PEBAX®),ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE),Marlex high-density polyethylene, Marlex low-density polyethylene,linear low density polyethylene (for example REXELL®), polyester,polybutylene terephthalate (PBT), polyethylene terephthalate (PET),polytrimethylene terephthalate, polyethylene naphthalate (PEN),polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI),polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (for example, KEVLAR®), polysulfone,nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon),perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin,polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions of the ablation device 120 mayalso be doped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of the ablation device 120 in determining its location. Someexamples of radiopaque materials can include, but are not limited to,gold, platinum, palladium, tantalum, tungsten alloy, polymer materialloaded with a radiopaque filler, and the like. Additionally, otherradiopaque marker bands and/or coils may also be incorporated into thedesign of the ablation device 120 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility may be imparted into the ablation device 120. For example,portions of device, may be made of a material that does notsubstantially distort the image and create substantial artifacts (i.e.,gaps in the image). Certain ferromagnetic materials, for example, maynot be suitable because they may create artifacts in an MRI image. Insome of these and in other embodiments, portions of the ablation device120 may also be made from a material that the MRI machine can image.Some materials that exhibit these characteristics include, for example,tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such asELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenumalloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, andthe like, and others.

The entire disclosures of the following documents are hereinincorporated by reference in their entirety:

U.S. patent application Ser. No. 13/750,879, filed on Jan. 25, 2013, andentitled “METHODS AND APPARATUSES FOR REMODELING TISSUE OF OR ADJACENTTO A BODY PASSAGE”.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A medical device for nerve ablation, comprising:a catheter shaft; an expandable member coupled to the catheter shaft,the expandable member having a proximal region, a distal region, and abody extending therebetween, the expandable member being a balloon; andan electrode support coupled to the catheter shaft and positioned overthe body of the expandable member, the electrode support including aplurality of spaced apart flexible elongate members, each having adistal end, a proximal end, and a body extending therebetween, and aplurality of electrode assemblies disposed on the electrode support, theelectrode support capable of expanding with the expandable member,wherein the electrode support is free from attachment with the body ofthe expandable member and wherein the plurality of spaced apart flexibleelongate members are connected to each other at their proximal anddistal ends, wherein the plurality of spaced apart flexible elongatemembers extend in a helix over the body of the expandable member.
 2. Themedical device of claim 1, wherein each of the plurality of spaced apartflexible elongate members includes at least two of the electrodeassemblies in a spaced apart arrangement.
 3. The medical device of claim1, wherein the electrode support includes a proximal section, whereinthe electrode support and the expandable member are attached to eachother only at the proximal section of the electrode support and theproximal region of the expandable member.
 4. The medical device of claim1, wherein the electrode support includes two or more spaced apart setsof three of the plurality of spaced apart flexible elongate members,wherein each of the spaced apart sets includes a first spaced apartflexible elongate member carrying active electrodes, a second spacedapart flexible elongate member including one or more temperaturesensors, and a third spaced apart flexible elongate member carryingground electrodes.
 5. The medical device of claim 1, wherein at leastsome of the plurality of electrode assemblies include a pair of bipolarelectrodes.
 6. The medical device of claim 1, wherein at least some ofthe plurality of electrode assemblies include a temperature sensor. 7.The medical device of claim 6, wherein the temperature sensor ispositioned between a bottom surface of one of the plurality of electrodeassemblies and an outer surface of the expandable member.
 8. The medicaldevice of claim 1, wherein the expandable member includes one or morechannels in an outer surface extending from a distal region to aproximal region of the expandable member.
 9. The medical device of claim1, wherein the expandable member is a compliant balloon.
 10. The medicaldevice of claim 1, wherein the expandable member is a non-compliantballoon.
 11. The medical device of claim 1, wherein the expandablemember has one or more channels extending along the body, the one ormore channels positioned between the plurality of spaced apart flexibleelongate members.
 12. A medical device, comprising: a catheter shaft; anexpandable balloon having a distal waist, proximal waist, and a bodyextending therebetween, the proximal waist being coupled to the cathetershaft; a flexible elongate electrode assembly coupled to the cathetershaft and extending in a helix over the body of the expandable balloon,the electrode assembly being free from attachment to the body of theexpandable balloon, the elongate electrode assembly comprising aplurality of spaced apart elongate members each having a distal region,a proximal region, and a body extending therebetween; a plurality ofelectrodes disposed on at least a first one of the plurality of spacedapart elongate members; and one or more elongate supports having adistal region, a proximal region, and a body extending therebetween, theone or more elongate supports extending in a helix over the body of theexpandable balloon and spaced apart from the plurality of spaced apartelongate members.
 13. The medical device of claim 12, wherein theplurality of spaced apart elongate members include three spaced apartelongate members and wherein the three elongate members are free fromattachment to each other along their respective bodies.
 14. The medicaldevice of claim 12, wherein the one or more elongate supports areconnected to the plurality of spaced apart elongate members only attheir distal and proximal regions.
 15. The medical device of claim 14,further comprising a first circuitry and a second circuitry connected tothe electrode elements, wherein the first circuitry extends proximallyalong the first one of the plurality of spaced apart elongate members,wherein the second circuitry extends distally along the first one of theplurality of spaced apart elongate members to a first one of the one ormore elongate supports, the second circuitry then extending proximallyalong the first one of the one or more elongate supports.
 16. A medicaldevice, comprising: a catheter shaft; an expandable balloon having adistal waist, proximal waist, and a body extending therebetween, theproximal waist being coupled to the catheter shaft; a flexible elongateelectrode assembly coupled to the catheter shaft and extending in ahelix over the body of the expandable balloon, the electrode assemblyfree from attachment to the body of the expandable balloon, wherein theelongate electrode assembly includes three spaced apart elongate memberseach having a distal region, a proximal region, and a body extendingtherebetween, and wherein the three spaced apart elongate members arefree from attachment to each other along their respective bodies; aplurality of electrode elements disposed on the flexible elongateelectrode assembly; and one or more elongate supports each having adistal region, a proximal region, and a body extending therebetween, theone or more elongate supports extending in a helix over the body of theexpandable balloon and spaced apart from the three spaced apart elongatemembers, the one or more elongate supports connected to the three spacedapart elongate members only at their distal and proximal regions. 17.The medical device of claim 16, further comprising a first circuitry anda second circuitry connected to the electrode elements, wherein thefirst circuitry extends proximally along a first one of the three spacedapart elongate members on which at least a portion of the plurality ofelectrode elements reside, wherein the second circuitry extends distallyalong the first one of the three spaced apart elongate members on whichat least a portion of the plurality of electrode elements reside to afirst one of the one or more elongate supports, the second circuitrythen extending proximally along the first one of the one or moreelongate supports.
 18. A method for treating hypertension, the methodcomprising: advancing a medical device in accordance with claim 1through a blood vessel to a position within a renal artery; expandingthe expandable member, thereby expanding the electrode support;energizing the electrode assemblies; collapsing the expandable member,and thereafter, withdrawing the expandable member and the electrodesupport into a delivery sheath, thereby collapsing the electrodesupport.